Central Dogma

processing mRNA

• RNA is copied directly from DNA - both introns and exons. After that it is processed in the nucles:

  • add modifications to either end that aid in stability

  • cut out the introns, splice together the exons

• the processed mRNA then leaves the nucleus and is read by the ribosome

not all genes code for _____

protein

RNA polymerase

• DNA codes for protein using a protein enzyme

• this makes a single-stranded RNA copy called mRNA (messenger RNA)

Universal code

• mRNA is read by the ribosome using 3 nucleotides = 1 codon per amino acid

• the codon code is degenerate ( > 1 code can result in the same amino acid for most amino acids)

• it is also universal

what is the start codon?

AUG

What protein does AUG code for?

methionine

when does the process stop?

when a STOP codon is hit

transfer RNA (tRNA)

• carry amino acids on one end and bind mRNA on the other end (anticodon of tRNA binds to codon on mRNA)

first step of ribosomes assemble proteins

• ribosomes assembles at first codon after first transfer RNA with first amino acid bound find the first codon.

• note - start codon is always 5’ AUG 3"‘ which codes for methionine

• note - also first codon not at very 5’ end of mRNA

second step of ribosomes assemble proteins

• new tRNA come into A site

• if a codon on mRNA matches anticodon on mRNA, it adds the amino acid

• no match - tRNA bounces out and try again

• once an amino acid is added the whole ribosome moves 1 amino acid toward 3’ end of mRNA

third step of ribosomes assemble proteins

• when a stop codon is reached, the ribosome comes apart and the protein is released to be folded

• the mRNA can be reused

steps of central dogma

1) DNA strucutre and regulation

2) transcription

3) RNA processing

4) translation

6) protein synthesis

7) reading frame

two parts of the central dogma

• nucleus

• cytoplasm

the first three steps of central dogma happen in the _____

nucleus

the last three steps of the central dogma happen in the. _____

cytoplasm